Apparatus for low-temperature refrigeration



Patented July 27, 1954 UNITED STAlS ATENT OFFICE APPARATUS FOR LOVlf-TEMIERATURE REFRIGERATION Application June 4, 1951, Serial No. 229,726

12 Claims.

This invention has to do with apparatus for low temperature refrigeration and it is a general object of the invention to provide apparatus that is effective and dependable for obtaining and maintaining temperatures well below those obtainable with ordinary or conventional refrigerating equipment.

Where very low temperatures are desired it is common to provide refrigerating systems in which compressors are compounded and heretofore attempts have been made to utilize the compressed rerfigerant through refrigerating units similar to those ordinarily ernpoyed in refrigeration and characterized by an expansion valve thermally controlled and supplying a coil, or the like. It has been found that such equipment does not always operate satisfactorily since the expansion valves, as ordinarily controlled, are not suficiently sensitive to varying conditions, and as a result the coils become starved for refrigerant and the temperatures obtained fluctuate.

It is general object of this invention to provide refrigerating apparatus in which a refrigerating unit is supp'ied with compressed refrigerant and involves an expansion valve that may be thermally controlled in the manner common to refrigerating apparatus and in which a supplemental supply of refrigerant is provided in such a manner to overcome or to avoid starving of the refrigerant unit as occurs when the expansion valve alone is relied upon for refrigerant.

A further object of the invention is to provide apparatus of the general character referred to in which control for the supplemental or auxiliary supply of refrigerant is responsive to conditions prevailing in the system or apparatus a point where substantial fluctuations occur, to

the end that it is possible to maintain uniformV operation.

In the apparatus provided by the present invention a unit is provided to utilize compressed refrigerant and may serve to chill a chest or the like. The unit may involve an expansion valve and a coil, or like element, utilizing the refrigerant, and further, it may include a ther- 'mal control regulating or operating the expansion valve. The system as provided by the invention further includes multiple compressors, for eigarnple, a low pressure compressor and a high pressure compressor connected bya refrigerant flow line and in accordance with conventional practice the outlet from the high pressure coinpresser4 is delivered to a heat exchanger from which the rerfigerant passes to a receiver. The receiver delivers the compressed refrigerant to a supply line which extends to and supplies the expansion valve of the refrigerati'ng unit. A thermally controlled bypass is provided, utilizing refrigerant from the supply line to cool the refrigerant flowing between the compressors. The invention provides an auxiliary control for the refrigerating unit responsive to pressure conditions prevailing in the system where refrigerant is under pressure, preferably between the cornpressors. The auxiliary control involves, generally, a bypass connection between the supply line and the intake of the coil, which connection bypasses the expansion valve. A control valve is provided in the bypass and a ow control or retarding device is connected in series with the control valve. A control means for the control vave preferably includes a thermally responsive unit in the area or chest being cooled, operating to regulate an operating circuit that extends to a motor that operates a variable contact ina contact mechanism operated in response to pressure in the refrigerant flow line that occurs between the compressors. The motor varies the setting of the contact mechanism under predetermined conditions. The Contact mechanism controls a circuit to an operating unit that causes operation of the valve in the bypass.

The various objects and features of our invention will be fully understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the accompanying drawings, in which:

Fig. 1 is a general diagram illustrating apparatus embodying the invention. Fig. 2 is an enlarged diagrammatic view of the thermally responsive unit that may occur in the chest or refrigerated area, and Fig. 3 is a diagrammatic view illustrating the relationship of the motor, the adjustable switch mechanism, and thepressure responsive unit that operates the switch mechanism.

The apparatus, as illustrated 'in the drawings, involves, generally, a unit A handling compressed refrigerant, which unit may be related to an area or structure to be refrigerated. In the case illustrated it is shown related to a chest B and it is shown involving, generally, an expansion valve il), a coil il in the chest B and a control means l2 thermally related to the other elements just mentioned and serving to operate the expansion valves. The apparatus further involves aprirnary or low pressure compressor C, a secondary or high pressure compressor D, and a refrigerant owI line E conducting compressed refrigerant from compressor C to compressor D. A delivery line F' conducts finally compressed refrigerant from compressor D to a heat exchanger H and the heat exchanger I-I delivers the refrigerant to a receiver J. The receiver supplies refrigerant to a supply line K that conducts the refrigerant to the unit A where it supplies the expansion valve Ill. A thermally responsive bypass means L is connected between the supply line K and the flow line E so that refrigerant is added to the flow line to cool the refrigerant passing between the compressors. An auxiliary control is provided in connection With the unit A and involves, generally, a refrigerant bypass M connected between the supply line K and the intake to the coil l i around the valve Hi, a control valve N in the bypass M, and a control system P which may involve, generally, a thermally responsive unit controlling a circuit carried by lines 2l and extending to a motor 22 which regulates a switch mechanism 28 operated by a pressure responsive unit 29 related to the line E. The switch mechanism 28 controls a circuit carried by lines controlling operating means 2S for the valve N.

As a typical application or adaptation of the apparatus the chest B is shown as carrying or having the coil il located therein and the thermally responsive unit 2!! is likewise located in the chest. The expansion valve lli of unit A may be a typical or standard type of expansion Valve receiving compressed refrigerant from supply line K and delivering it to the inlet line it that connects the valve IU and the coil H. The outlet line 3l from the coil il is shown extending from the chest to the intake of compressor C.

The control means I2 of unit A may be any ordinary or conventional control arrangement, for example, as shown in the drawings, it may involve a thermally responsive unit it related to the line 3| or otherwise related to the coil of the chest B to be responsive to the action of the coil or the condition prevailing in the chest. A suitable operating connection t! extends from the unit il@ to the expansion valve lil to effect operation thereof. With the control l2 just described and Which may be any ordinary or conventional control found in apparatus of this general character, it is common for the temperature conditions to vary in the chest B due to the coil Il being starved for refrigerant and the control I2 and valve i9 failing to respond rapidly enough to maintain a substantially constant condition in the coil and chamber B.

The low pressure compressor C receiving re frigerant from the exhaust line 3l may be driven by a motor @l5 and serves to deliver compressed refrigerant to the refrigerant now line E. The line E is shown extending directly from compressor C to the intake of compressor D which is a high pressure compressor driven by a motor 46. The outlet or delivery line F of compressor D extends to the heat exchanger H which may be any conventional heat exchanging apparatus that cools the compressed refrigerant and delivers it to the receiver J. The receiver J holds a suitable supply of refrigerant and serves the supply line K which conducts the compressed cooled refrigerant to the expansion valve lli.

The bypass means L shown in the diagram involves a bypass line 5t from the supply line K to the flow line E which bypass is under control of a valve 5I. The control means for the valve 5| involves a thermally responsive unit 52 responding to the temperature of the refrigerant in the line E and an operator 515 for Valve 5l connected with the unit 52 by an operating cir cuit carried by lines 55. With the bypass means il a portion of the compressed refrigerant from supply line K is returned to the system at the line E to cool the refrigerant passing from compressor C to compressor D.

The auxiliary control, as provided by the present invention, involves the bypass line or connection M that connects supply line K and the intake line 3? to the coil l l around the expansion valve I. The control valve N is provided in the line lVi and is operated by the operating unit 2% shown in this case as an electrically actuated unit. In practice itis desirable to provide a valve N which operates between a fully open and a fully closed position, in which case a ow retarding means is provided in the bypass line M in the form of a ow restricting tube til, or the like. Any suitable flow controlling device or restricting device, such as an orifice fitting or regulating valve, can be employed in place of the tube, as shown in the diagram.

The valve N that controls the bypass connection lVi is operated in response to the temperature conditions prevailing in the chest B. In the arrangement illustrated a thermally responsive unit :2li provided in or suitably located with relation to the chest B and operates in response to changes in temperature in the chest. ln the case illustrated the unit 2li is shown as involving a thermally responsive device 24 operating a circuit regulator or resistance unit 23 in a circuit carried by the lines Zi which extend to the motor 22. The motor 22 is operatively connected with an adjustable or regulable contact l@ of the switch mechanism 2S. A second contact "il of the switch mechanism 23 is operated by the pressure responsive unit Ze which is subject to the pressure prevailing in line E. From the drawings it will be apparent that variation in temperature occurring in the chest B varies the circuit 2i so that the motor 22 shifts or regulates the position of contact lll. When pressure occurs in the line E to move the contact ll into engagement with the contact lil the mechanism Z8 is operated so that the circuit controlled thereby is closed. The circuit controlled by the mechanism 28 is an electric circuit carried by lines 25 and controls the operation of the operating unit 25 that operates valve N. in the case illustrated when the switch mechanism 28 is closed the valve ri is opened. Through the auxiliary control above described a very accurate or delicate regulation can be obtained, The pressure or temperature condition prevailin the outlet line 5l from the coil il reects the condition of operation of the coil or the temperature in the chest B but the variations are not such as to make practical delicate regulation of the valve El). The variation in pressure that occurs in line 3i is multiplied many times in the line E in that the compressor C will, in an ordinary situation, have a compression ratio of about one to ten, all of which results in the pressure variation in line E being ten times as great as that occurring in line 3i. Such magnied pressure variation results in operation of the pressure responsive unit 29 in a manner to cause rapid and sensitive response to pressure changes, to the end that the valve N is opened immediately that the coil l i starts to be starved for refrigerant. When the valve N is opened the refrigerant is bypassed around the expansion valve l0 and the supply of refrigerant passed by the valve it is supplemented by that passed by the valve N, with the result that an adequate supply of refrigerant is immediately available in the coil 1H. As the pressure drops due to the adequate supply yof refrigerant the control system operates and closes the valve N until a starved condition of the coil i i again develops.

Having described only a typical preferred form and application of our invention, We do ynot wish to be limited or restricted to the specific details herein set forth, but wish to reserve to ourselves any variations or modifications that may appear to those skilled in the art and fall within the scope of the following claims.

Having described our invention, we claim:

1. In combination, a refrigerant handling unit including, an expansion valve, a coil supplied by the valve, and a control for the valve including a 'thermally responsive element and an operating connection between said element and the valve, a refrigerant compressor receiving :refrigerant from the coil, a refrigerant supply line extending from the compressor to said coil, said valve being interposed in the sup-ply line, and a refrigerant control including a bypass around the said valve and vconnected to supply line upstream and downstream of the valve, between the valve and and means controlling now through the bypass responsive to pressure of refrigerant delivered by the compressor, said flow control means including a pressure esponsive control valve in said by-pass.

2. in combination, a refrigerant handling unit including, an expansion valve, a coil supplied by the valve, and a control for the valve including a thermally responsive element and an operating connection between. said element and the valve, a primary refrigerant compressor receiving refrigerant from the coil, a refrigerant supply,T line extending from the compressor to said coil, said valve being interposed in the supply line, a secondary refrigerant compressor, a flow line from the outlet of the primary compressor to the intake of the secondary compressor, and a refrigerant control including a bypass around the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means controlling flow through the bypass responsive to pressure of refrigerant in the flow said liow control means lincluding a pessure responsive control valve in said bypass.

S. In combination, a refrigerant handling unit including, expansion valve, a coil supplied by the valve, and a control for the valve including a thermally responsive element and an operating connection between said element and the valve, a refrigerant compressor receiving refrigerant from the a refrigerant supply line extending from the compressor' to said coil, said valve being interposed the supply line, and a refrigerant control including a bypass around the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means controlling flow through the bypass responsive to pressure of refrigerant delivered by the compressor through said supply line and including, a pressure responsive control valve in the bypass, and a pressure responsive element operated by pressure delivered by the compressor and governing operation of the control valve.

4. In combination, a refrigerant handling unit including, an expansion valve, a coil supplied by the valve, and a control for the valve including a thermally responsive element and an operating connection between said element and the valve, a refrigerant supply line extending from the com- -pressor to said coil, said valve being interposed in the supply line a refrigerant compressor receiving refrigerant from the coil, and a refrigerant `control including a kbypass around the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means controlling now through the bypass responsive to pressure of refrigerant delivered by the compressor and including, a pressure responsive control valve in the bypass, a flow retarding element the bypass downstream of said control valve, and a pressure responsive element operated by pressure delivered by the coin- Ipresser and governing operation of the control valve.

5. In combination, a refrigerant handling unit including, an expansion valve, a coil supp-lied by the valve, and a control for the valve including a thermally responsive element and an operating connection between said element and the valve, a refrigerant supply line extending from the coinpresser to said coil, said valve being interposed in the supply line a refrigerant compressor receiving refrigerant from the coil, a heat exchanger receiving refrigerant from said compressor, and a refrigerant control including a bypass laround the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means controlling flow through the bypass responsive to pressure of refrigerant delivered by the cornpressor and including, a pressure responsive con trol valve in the bypass, an operator for the control valve, and a pressure responsive element located upstream of said heat exchanger and operated by pressure from the compressor and controlling operation of the said operator.

In combination, a refrigerant handling unit including, an expansion valve, a coil supp-lied by the valve, and a control for the valve including a thermally responsive element and an operating connection between said elementfand the valve, a refrigerant compressor receiving refrigerant from the coil, a refrigerant supply line exten-:ling from lthe compressor to said coil, said valve being interposed in the supply line, and a refrigerant control including a bypass around the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means contro1 ng iiow through the bypass responsive to pressure of refrigerant delivered by the compressor including, a pressure responsive control valve in the bypass, an operator for the control valve, an adjustable pressure responsive element operated by pressure from the compressor and controlling operation of the said operator, and a thermally responsive element operative in response to variations in the temperature of the refrigerant from the coinpressor to adjust the pressure responsive elenien 7. In combination, a refrigerant handling unit Acluding, an expansion valve, a coil supplied by the valve, and a control for the valve including a thermally responsive element and an operating connection between said element and the valve, a refrigerant compressor receiving` refrigerant fromA the coil, a refrigerant supply line extending from the compressor to said coil, said valve being interposed in the supply line, and a refrigerant control including a bypass around the said valve and connected to said supply line upstream and downstream of the valve, between the valve and the coil, and means controlling flow through the bypass responsive to pressure of refrigerant delivered by the compressor and including, a pressure responsive control valve in the bypass, an

operator for the control valve, a pressure responsive element operated by pressure from the compressor and controlling operation of the said operator, and means varying action of the pressure responsive element in accordance with temperature changes of the refrigerant delivered by the compressor including, a variable switch controlling an operating circuit to the control valve and a thermally responsive element varying a control circuit to the switch.

8. ln combination, a refrigerant handling unit including, an expansion valve, a coil fed by the valve, and a thermally responsive control governing the expansion valve, a, refrigerant compressor receiving refrigerant from the coil and delivering it compressed, a heat exchanger cooling the compressed refrigerant, a supply line conducting the cooled compressed refrigerant from the exchanger to the expansion valve, a bypass line extenoing around the expansion valve with its ends connected to said supply line respectively upstream and downstream of the valve, between the valve and the coil, a pressure responsive control valve in the said bypass, an electric operator for the control valve, a variable switch controlling the operator, and a pressure responsive unit operating the switch and actuated pressure from the compressor.

9. In combination, a refrigerant handling unit including, an expansion valve, a coil fed by the valve, and thermally responsive control govrning the expansion valve, a refrigerant cornpressor receiving refrigerant from the coil and delivering it compressed, a heat exchanger cooling the compressed refrigerant, a supply line conducting tlie cooled compressed refrigerant from the exchanger to the expansion valve, a bypass line extending around the expansion valve with its ends connected to said supply line respectively upstream and downstream of the valve, between the valve and the coil, a pressure responsive control valve in the d bypass, an electric operator for the control valve, a variable switch controlling the operator, a thermally responsive element regulating the switch, and a pressure responsive unit operating the switch and actuated by pressure the compressor.

1G. in combination, a refrigerant handling unit including, expansion valve, a coil fed by the valve, and a thermally responsive control governing the expansion valve, a refrigerant compressor receiving refrigerant from the coil and delivering it compressed, a heat exchanger cooling the cornpressed rei'gerant, a supply line conducting the cooled compressed refrigerant from the exchanger to the expansion valve, a bypass line extending around the expansion valve with its ends connected to said supply line respectively upstream and downstream of the valve, between the valve and the coil, a pressure responsive control valve in the said bypass, a flow retarding means in the bypass downstream of said control valve, an electric operator for the control valve,

an adjustable switch controlling the operator, a thermally responsive element regulating the switch, and a pressure responsive unit operating the switch and actuated by pressure from the compressor.

ll. n combination, a refrigerant handling unit including, an expansion valve, a coil fed by the valve, and a thermally responsive control governing the expansion valve, a low pressure refrigerant compressor receiving refrigerant from the coil and delivering it compressed, a high pressure refrigerant compressor, a flow line conducting refrigerant from the low pressure compressor to the high pressure compressor, a heat exchanger cooling the compressed refrigerant from the high pressure compressor', a supply line conducting the cooled compressed refrigerant from the exchanger to the expansion valve, a bypass line eX- tending around the expansion valve with its ends connected to said supply line respectively upstream and downstream of the valve, between the valve and the coil, a pressure responsive control valve in the said bypass, and means operating the control valve in response to variations in the pressure of refrigerant in said now line.

l2. In combination, a refrigerant handling unit including, an expansion valve, a coil fed by the valve, and thermally responsive control goverrnng the expansion valve, a low pressure refrigerant compressor receiving refrigerant from the coil and delivering it compressed, a high pressure refrigerant compressor, a flow line conducting refrigerant from the low pressure compressor to the high pressure compressor, a heat eX- changer cooling the compressed refrigerant from the high pressure compressor, g supply line conducting the cooled compressed refrigerant from the exchanger to the expansion valve, a therrnally controlled bypass means conducting refrigerant from the supply line to the now line, a bypass line extending around the expansion valve with its ends connected to said supply line respectively upstream and downstream of the valve, between the valve and the coil, a pressure responsive control valve in the said bypass, and means operating the control valve in response to variations in the pressure of refrigerant in said flow line.

References Cited in the file of this patent UNTED STATES PATENTS Number Name Date 2,157,329 Fille May 9, 1939 2,237,574 Persons Apr. 8, 194i 2,289,923 Miller July 14, 1942 2,351,146 li/.lcCloy June 13, 1944 2,368,198 Dodson Oct. 9, 1945 2,454,253 Newton Nov. 16, 1948 2,519,495 Lange June 6, 1950 2,520,045 McGrath Aug. 22, 1950 2,523,451 Schulz et al. Sept. 26, 1950 2,540,550 Schulz et al. Feb. 6, 1951 

